Use of power spectral density in deriving response spectral shapes for aseismic design Original Research Article

Mean and mean + σ response spectral shapes based on accelerograms normalized to their respective peak ground acceleration (PGA) values have been widely used in the aseismic design of critical structures such as nuclear power plants. The computation of response spectral shapes based on accelerograms normalized to their respective power spectral densities (PSDs) has been proposed. A comparison of response spectral shapes using the two alternative normalization parameters (PGA and PSD) has been presented to demonstrate that the ordinates of the PSD-based mean + σ spectral shapes, which are better representatives of earthquake vibrations, are considerably lower than those of the PGA-based spectral shapes. The mean spectral shapes in the two cases are very close to each other, suggesting that a large part of the scatter in the PGA-based shapes is attributable to the procedure adopted for normalization of the accelerogram. The PSD-based spectral shapes can play an effective role in determining the margins available in the aseismic design of structures using the PGA-based mean + σ spectral shapes. Smooth response spectral shapes based on normalization with respect to the PSD are given for rock and soil sites at the end of the paper.